A conventional combustible gas turbine engine includes a compressor, a combustor, and a turbine. The compressor compresses ambient air. The combustor combines the compressed air with a fuel and ignites the mixture creating combustion products defining a working gas. The working gas travels to the turbine. Within the turbine are a series of rows of stationary vanes and rotating blades. Each pair of rows of vanes and blades is called a stage. Typically, there are four stages in a turbine. The rotating blades are coupled to a shaft and disc assembly. As the working gas expands through the turbine, the working gas causes the blades, and therefore the shaft and disc assembly, to rotate.
Combustors often operate at high temperatures. Typical combustor configurations expose turbine vanes and blades to these high temperatures. As a result, turbine vanes and blades must be made of materials capable of withstanding such high temperatures. In addition, turbine vanes and blades often contain internal cooling systems for prolonging the life of the vanes and blades and reducing the likelihood of failure as a result of excessive temperatures.
Typically, turbine vanes comprise inner and outer endwalls and an airfoil that extends between the inner and outer endwalls. The airfoil is ordinarily composed of a leading edge and a trailing edge. The vane cooling system receives air from the compressor of the turbine engine and passes the air through the airfoil. One example of a cooling system within a vane is disclosed in U.S. Pat. No. 6,254,334. The cooling system comprises a plurality of cooling circuits 26 incorporated within a wall of an airfoil to effect cooling of the airfoil wall.
Conventional turbine vanes have many different designs of internal cooling systems. While many of these conventional systems have operated successfully, the cooling demands of turbine engines produced today have increased. Thus, an internal cooling system for turbine vanes as well as blades having increased cooling capabilities is desired.